1. Field of the Invention
This invention relates to a diffusion transfer photographic film which provides an excellent print and which has excellent dimensional stability.
2. Description of the Prior Art
Recently, diffusion transfer photography enabling photographed pictures to be viewed on the spot has spread increasingly due to its convenience.
The structure of diffusion transfer photographic films, in particular, the structure of diffusion transfer color photographic films, more or less varies dependent upon the processes for developing and printing them as described in, for example, Properties of Films and Processing Arts Therefor (published by Shashin Kogyo Shuppan Sha, Oct. 15, 1976). In principle, however, the photographic film comprises the constituents necessary for photography, development and printing.
A detailed description and explanation of diffusion transfer photographic films are set forth below.
The so-called diffusion transfer process instant color photographic light-sensitive materials as well known as diffusion transfer photographic films in the photographic art. In these types of materials, diffusible dyes are image-wise released from a light-sensitive element in conformity with the images exposure. Of these materials, film units in which a development processing solution is spread as a thin layer immediately after photographing and which does not require the image-receiving layer to be separated from the light-sensitive element by, e.g., an operation such as delamination, and which permits the composite to be used as a photographic picture are advantageous since they have the advantages that they are handy, their procedure of use is simplified, the development processing solution is not uncovered and, therefore, clothes are not stained by the processing solution, and no waste materials due to delamination are produced. These composite film units are described in U.S. Pat. Nos. 2,983,605, 3,415,645, 3,415,646, 3,415,644, 3,578,540, 3,573,043, 3,615,421, 3,594,164, 3,594,165, 3,620,724, 3,635,707, 3,993,486, British Pat. Nos. 1,269,805, 1,330,524, etc., and are well known.
These composite film units contain, sandwiched between two dimensionally stable supports, light-sensitive silver halide emulsion layers, dye image-providing compounds associated with the silver halide emulsions, an image-receiving layer capable of fixing as an image the diffusible dyes released from the dye image-providing compounds, and a light-reflecting layer which serves as a white background for viewing the image formed in the image-receiving layer. In addition, a container retaining a processing solution is disposed at a given position between the two supports and which is capable of spreading a development-processing solution in a layer state thereon. These constituents are fixed together to form a composite structure. In a preferred embodiment, the film unit has, in sequence from the exposure side, a blue-sensitive silver halide emulsion layer having associated therewith a yellow dye image-providing compound, a green-sensitive silver halide emulsion layer having associated therewith a magenta dye image-providing compound and a red-sensitive silver halide emulsion layer having associated therewith a cyan dye image-providing compound between the two supports, with these silver halide emulsion layers being advantageously separated from each other by interlayers. In addition, the film unit advantageously contains a polymer acid layer for neutralizing alkali brought into the element with the processing solution after substantial completion of a dye image, and a neutralization timing layer for controlling the formation of an image and the rate of neutralization. Further, the film unit advantageously has a light-intercepting layer which permits the film unit to be processed in a bright room after the film unit comes out of the camera. Additionally, the supports may have a backing layer thereon. The most preferred film unit structure comprises, in sequence from the exposure side, (A) a transparent support--a polymer acid layer--a neutralization timing layer--an image-receiving layer--(a processing solution layer containing a light-reflecting material)--a protective layer--a blue-sensitive silver halide emulsion layer--a yellow dye image-providing compound layer--an interlayer--a green-sensitive silver halide emulsion layer--a magenta dye image-providing compound layer--an interlayer--a red-sensitive silver halide emulsion layer--a cyan dye image-providing compound layer--a light-intercepting support; or (B) a transparrent support--a polymer acid layer--a neutralization timing layer--(a processing solution layer containing a light-intercepting material)--a protective layer--a blue-sensitive silver halide emulsion layer--a yellow dye image-providing compound layer--an interlayer--a green-sensitive silver halide emulsion layer--a magenta dye image-providing compound layer--an interlayer--a red-sensitive silver halide emulsion layer--a cyan dye image-providing compound layer--a light-intercepting layer--a light-reflecting layer--an image-receiving layer--a transparent support. Film unit (A) described above is exposed through the transparent support, with the image formed being viewed through the same support, whereas film unit (B) described above is exposed through the transparent support adjacent the polymer acid layer, with the image formed being viewed through the transparent support adjacent the image-receiving layer.
The film unit constituents provided between the two supports are bound at the periphery thereof to maintain the composite film unit form prior to, during and after development processing and prevent the spread processing solution from oozing out of the unit, and the film unit is preferably constructed so that a definite space exists between the two supports in order to spread the processing solution in a given thickness. Further, the film unit preferably has a pod retaining the processing solution which is fixedly positioned at one end thereof and a reservoir for receiving excess processing solution which is fixedly positioned at the opposite end thereof. Various bonding or fixing techniques can be used. Typical examples include (i) adhering the two supports externally with a binding member which embraces the two supports (outer spacer) and (ii) adhering photographic layers between the two supports using a binding member (inner spacer).
FIGS. 1, 2 and 3 show examples of the structures of diffusion transfer photographic films, particularly of diffusion transfer color photographic composite film units. In these figures, the details of emulsion layers, although important in the photographic film, are not shown since they are not necessary to describe the invention, and as a result, these figures illustrate diagrammatic views mainly showing the elements necessary for describing the materials to which the present invention is applicable.
FIG. 1 shows a photographic film of type (A) described above in which the exposure side (A-1) and the print-viewing side (A-2) are on the same side, and FIG. 2 is an enlarged view thereof. In this type of film, transparent film support (1) is on the surface side and black opaque film support (2) is on the back side, with a border (4) of white contact-bonding tape (3). Pod (6) retaining processing solution (5) is attached to the back surface of the lower side of the image layer. Layers between supports (1) and (2) comprise emulsion layer (7), image-receiving layer (8), neutralizing layer (9) for neutralizing the processing solution and processing solution layer (10) to be formed by processing solution (5) released from pod (6) and spread on the image area, and the like. Another example is a photographic film of the type (B) described above wherein the exposure side (B-1) and the print-viewing side (B-2) are on opposite sides of the film as illustrated in FIG. 3. This type of film comprises transparent film supports (1) at the surface and the back side, neutralizing layer (9), processing solution layer (10) to be formed after photographing by processing solution (5) spread from pod (6), emulsion layer (7), light-intercepting black layer (11) and image-receiving layer (8).
After image-wise exposure, these photographic films are passed between rollers to rupture pod (6) retaining processing solution (5) and to spread processing solution (5) over the image area for conducting development and printing. When the photographic films come out of the camera, they are in a sufficiently dry state to be satisfactorily handled, and a printed image gradually becomes distinct to provide a photographic picture in about 5 to 10 minutes.
However, these convenient diffusion transfer photographic films have the following defects in handling after photographing.
(1) The printed surfaces must be handled with care for about 10 minutes after photographing.
(2) It takes such a long time for the water present in the processing solution or the like to escape as a vapor into the atmosphere that the photographic pictures do not easily dry. Thus, a long time is required before the image becomes completely stable.
(3) The photographic pictures obtained cannot be stored in a highly humid place due to reason (2) described above, and hence color change, deformation or blocking with other photographic pictures or with album mounts tends to occur during storage.
With the film unit of, in particular, the inner spacer type as hereinbefore described, the processing solution is not spread on the back of the binding member, and hence a difference occurs in that the central areas (image area) of the two supports come into contact with water of the processing solution, whereas the peripheral area (binding member area) does not come into contact with the water of the processing solution. If the supports are made of a material which will swell to a degree above a certain limit when in contact with water, the area which swells is enclosed in a non-swelling frame, resulting in a distortion of the film unit. With a film unit of the outer spacer type (i), a similar distortion can occur when the binding member is swollen only with difficulty with water and the mechanical strength thereof is larger than a certain limit.
Various techniques have been developed for removing these defects. For example, (1) choosing constituents including emulsion layers and the like of the film so as to minimize the amount of processing solution, and (2) use of a support film having a large water permeability as the surface layer and the back side layer of a photographic film have been suggested. With respect to approach (1) above, a large number of examinations have been made. However, removal of the above-described defects using this approach has not been sufficient. With respect to approach (2), cellulose triacetate films widely used as a support for motion picture film or photographic film have been examined. It is true that a cellulose triacetate film has excellent water permeability and permits water contained in a photographic film to escape as a vapor, but a cellulose triacetate film is not dimensionally stable under high humidity conditions so that the image surface becomes uneven during escape of water damaging the photographic values. Therefore, at present, unavoidably a polyethylene terephthalate film must be used due to its excellent flatness, dimensional stability under high humidity conditions, chemical resistance and transparency despite its unsatisfactory water permeability.
Stabilization of the image has been attempted by rapidly removing the solvent (in many cases water) of the processing solution from the composite film unit. For example, British Pat. No. 1,313,868 describes the use as a support of a polymer layer of cellulose acetate, regenerated cellulose, cross-linked polyvinyl alcohol, or an extremely thin polyester base, a polyester base containing pores permeable to water vapor (the vapor permeability being not less than 100 g/24 hrs.multidot.100 in.sup.2 /mil (corresponding to 394 g/24 hr.multidot.m.sup.2 /0.1 mm), preferably not less than 300 g/24hrs.multidot.100 in.sup.2 /mil (corresponding to 1182 g/24 hr.multidot.m.sup.2 /0.1 mm)). However, the polymer supports specifically described above are not satisfactory for use in a composite film unit due to one of the following defects: (1) the swelling when the polymer supports are in contact with water is so large that the film unit form will be affected when a development processing solution is spread; (2) the deficiency in mechanical strength due to the very thin thickness makes it difficult to coat a photographic layer thereon or to uniformly spread the processing solution; (3) the polyester base containing fine pores (e.g., having a size of 23-107 .mu.) is optically opaque, and hence image-wise exposure through such a support or viewing images through such a support is actually difficult. In particular, with a film unit having a structure where swelling with water is restricted by at least one end of the film unit, a dimensional lack of balance will occur between the image area which swells when in contact with water and the end area which does not swell even in contact with water where a weakly hydrophilic support like cellulose acetate as described above is used. In such a case, the film unit will be seriously deformed after spreading the processing solution, and this deformation remains even after the processing solution is dried away to such a degree that the resulting photograph cannot be satisfactorily utilized any more. In addition, supports with insufficient transparency cannot be used for film unit (B) described above which is a particularly preferable type.